Database Reference
In-Depth Information
Figure 1.23
The Music Studio
Schema Sales Data
Warehouse.
house data model should in its ideal form be in the structure of a star (star
schema) or in a less ideal form of a degraded star schema (snowflake). In
Figure 1.23 the SALES table is the fact table, and all other tables are
dimensions of those sales entries. The schema represented by the entity
relationship diagram is in fact a snowflake schema because of the relation-
ship between the CONTINENT and COUNTRY tables. This relation-
ship is not strictly necessary, but it was useful during the process of
writing this topic.
Dimension Tables
. RETAILER, CONTINENT, and COUNTRY
are all purely dimensional entities of SALES.
Partial Dimension Tables
. The CUSTOMER table could be con-
strued as being a partial fact table describing SALES table entries,
apart from the fact that there is a link to the GENRE table in the
OLTP structure. Links are shown in Figure 1.24.
Fact Tables
. The SALES table is a fact table because it contains facts
about sales or, more simply put, sales transaction records. All dimen-
sions describe SALES such as what country a sale occurred in.
